As wireless electric power supply techniques, techniques using electromagnetic induction and techniques using radio waves are known. On the other hand, recently, techniques using a magnetic field resonance mode have been proposed.
Japanese Laid-open Patent Publication No. 2009-501510 discusses the wireless electric power supply techniques using the magnetic field resonance mode, a resonator with a resonance frequency fr1 is provided in a power transmitting device and a resonator with a resonance frequency fr2 is provided in a power receiving device. By tuning these resonance frequencies fr1 and fr2 to each other and adjusting the sizes and the arrangement of the resonators adequately, a coupled state of magnetic fields, in which energy may be transferred by using the magnetic field resonance mode, occurs between the power transmitting device and the power receiving device, and electric power is transmitted from the resonator provided in the power transmitting device to the resonator provided in the power receiving device. According to such wireless electric power supply techniques, electric power transmission efficiency (energy transfer efficiency) may reach about several tens of percent. Also, the distance between the power transmitting device and the power receiving device may be extended to a relatively large value, for example, several tens of centimeters for resonators having a size of several tens of centimeters.